Plant hormones, and the control of growth

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  • control of plant growth
    • Gravitropism
      • growth in responses to the direction of light.
      • Positive gravitropism
        • The root tip grows towards gravity so there is more chance of finding moisture.
      • Negative gravitropism
        • In the stem tip to go away from the force of gravity , so there is more chance of finding light.
    • Phototropism
      • Growth in response to the direction of light.
      • Positive Phototropism
        • Is in the stem tip so the shoot grows towards the light, to get maximum light for photosynthesis
      • Negative phototropism
        • This is in the root tip to stop it from growing towards the light and drying out.
    • "Tropism" is a growth in response to a stimulus.
      • Plants grow towards, gravity, light and moisture.
      • Positive tropism is where it grows towards the stimulus
      • Negative tropism is away from the stimulus.
    • Auxin
      • It is a plant hormone produced by in the stem tips and roots, which controls the direction of growth.
      • Auxin gathers on the lower side of the root and stem.
      • In the root it grows more on the side with the least auxin making it bend and grow towards gravity.
        • Once it has grown down the auxin becomes evenly spread again.
      • In the shoot it grows more in the side with the most auxin, so it bends and grows up and away from the force of gravity.
        • When it has grown up the auxin becomes evenly spread again.
      • Auxin changes the elasticity of the cells
        • The more elastic the cells are the more they grow and absorb more water.
          • causing bending.

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